1. Technical Field
The present invention relates to a reflection-type electro-optical device and an electronic device that includes the electro-optical device.
2. Related Art
As one of various electro-optical devices, a reflective liquid crystal device includes a pair of substrates with a liquid crystal layer interposed therebetween, a reflective electrode disposed on one of the substrates, and a translucent electrode disposed on the other of the substrates. One of the reflective electrode and the translucent electrode constitutes a pixel electrode, and the other constitutes a common electrode. In such an electro-optical device, the reflective electrode is formed of a metallic material, such as an aluminum material or a silver material, and the translucent electrode is formed, for example, of indium tin oxide (ITO). The reflective electrode desirably has a high reflectivity. However, the formation of a high-refractive index layer, such as an alignment film, on the reflective electrode reduces the reflectivity. Thus, Japanese Patent Application Publication No. 11-2707 proposes forming a reflectance improver film formed of a plurality of dielectric films on a reflective electrode.
In electro-optical devices, an alternating-current electric field is applied to a liquid crystal layer through a reflective electrode and a translucent electrode. Since a pixel electrode and a common electrode have different work functions, the electric field applied to the liquid crystal layer is asymmetrical. For example, ITO of a translucent electrode has a work function of approximately 5.0 eV, whereas aluminum of a reflective electrode has a work function of approximately 3.2 eV. Thus, in an electro-optical device, displaying a certain pattern for a long period of time often causes failures, such as burn-in. Such failures also occur in an electro-optical device that has a reflectance improver film formed of a dielectric multilayer film on a reflective electrode, as described in Japanese Patent Application Publication No. 11-2707. To prevent burn-in, the voltages applied to the reflective electrode and the translucent electrode are often offset to secure symmetry of the electric field applied to the liquid crystal layer. However, the symmetry may be lost owing to ambient temperature variations or time-dependent changes.